Introduction An 1-year-old boy is brought to the emergency department by his parents due to increased irritability and an "enlarging head." The parents deny any trauma but has noticed their infant appears weaker than his sister when she was his age. They did not receive adequate prenatal care due to the distance and cost to arrive to their closest obstetrician. On physical exam, the infant is inconsolable and has an increased head circumference for his age. Magnetic resonance imaging (MRI) of the head shows hypoplasia of the cerebellar vermis with cystic dilatation of the fourth ventricle leading to a non-communicating hydrocephalus. Introduction Clinical definition a neurological developmental anomaly of the cerebellar vermis and failure of proper closure of the fourth ventricle which results in an abnormally large posterior fossa Epidemiology incidence 1 in 30,000 births Associated conditions noncommunicating hydrocephalus spina bifida Presentation Symptoms intellectual or learning disability seizures issues with movement coordination mood Physical exam macrocephaly if hydrocephalus ensues may have spastic paraplegia Imaging Prenatal ultrasound indication used when a CNS malformation is suspected to diagnose Dandy-Walker malformation other imaging modalities are used to diagnose Dandy-Waler malformation such as fetal MRI and post-natal CT of the head findings dilatation of the fourth ventricle presistent Blake's pouch cyst enlargement of the posterior fossa MRI indication imaging of choice for assessing for Dandy-Walker malformation findings hypoplasia of the cerebellar vermis cystic dilatation of the fourth ventricle posterior fossa enlargement Treatment Conservative multidisciplinary team indication a multidisciplinary team approach is warrented in the management of Dandy-Waler malformation this includes special education physical therapist social services neurologists genetic counselors Operative ventriculoperitoneal shunting indication used to treat hydrocephalus